1. Field of the Invention
The present invention relates to a nitride semiconductor substrate and to a method for working a nitride semiconductor substrate.
2. Related Background Art
Various kinds of gallium nitride substrate (GaN substrate) have been known in the past (see Japanese Laid-Open Patent Applications 2003-183100, 2004-335645, and 2000-12900). Japanese Laid-Open Patent Application 2004-335645 discusses a gallium nitride wafer having an orientation flat (OF) as a mark indicating crystal orientation. This orientation flat is formed by first confirming the crystal orientation by X-ray diffraction, and then grinding the wafer.
Japanese Laid-Open Patent Application H7-307316 discusses a method for forming an orientation flat on a wafer composed of a semiconductor compound other than GaN, such as GaAs, GaP, or InP. Japanese Laid-Open Patent Application H2-291146 discusses a method for detecting the position of an orientation flat formed on a wafer.